Floodlights, new River players make for Copa Libertadores knockout drama

Ignacio Scocco scored the first of River Plate's goals as they took a big step toward the quarterfinals.

It is a new Copa Libertadores with a fresh calendar -- and some of the same old problems. The match between Guarani of Paraguay and Argentina's River Plate suffered an 11-minute hold up because of an old fashioned floodlight failure -- not an uncommon event at Asuncion's Defensores del Chaco Stadium.

This was always a game likely to generate more heat than light, though, for two reasons.

One was the fact that two River Plate players tested positive in post-match drug tests towards the end of the group phase. Centre-back Lucas Martinez Quarta and midfielder Camilo Mayada were both handed suspensions. But there were rumours of something more sinister afoot -- that other players might also be affected as a consequence of a mistake in the club's medical department, who might have handed out a contaminated food supplement.

If more than two players test positive, the doors are open to a collective punishment suffered by the club. CONMEBOL announced Tuesday that all of the River Plate team would be tested at the conclusion of the match against Guarani.

The other bone of contention was the issue of reinforcements. Originally the competition regulations stated that three changes could be made to squads at this stage of the tournament, going into the knockout phase. A late announcement was then made, authorising six changes. The main beneficiaries of the increase are River Plate, who have drafted in four high-profile players.

Guarani, who lost their main attacking talent, Nestor Camacho, to local rivals Olimpia, were unhappy that the regulations had been altered and attributed the late change to behind-the-scenes lobbying from River Plate.

The Buenos Aires giants denied their influence, but there is no doubt that the increase works in their favour. Goalkeeper German Lux and World Cup midfielder Enzo Perez have yet to be introduced to the team. But the other two vastly experienced reinforcements did play in Asuncion.

Adventurous centre-back Javier Pinola helped set River's attacks in motion, and one-time Sunderland striker Ignacio Scocco played a decisive role. With the aid of a wicked deflection, his first-half free kick -- just before the floodlight failure -- gave River the lead.

In the closing stages Marcelo Larrondo headed in a second, leaving the Argentines in a very strong position. Guarani will have to come up with one of the biggest shocks in the history of South American club football in Buenos Aires next month if they are to prevent River Plate from reaching the quarterfinals.

Ramiro's goal in the first minute was all Gremio would need to prevail on Tuesday.

Assuming they cruise safely into the last eight, River might well have the opportunity to prevent an all-Brazilian final. Six Brazilian sides are in the last 16, but five of them are in one half of the draw. The exception is Atletico Mineiro, favourites to overcome Jorge Wilstermann of Bolivia, this year's surprise side. Should their respective ties go with form, then River Plate and Atletico will meet in the quarterfinal -- where an Argentine win would end the possibility of a final between two Brazilian clubs.

There already seems very little possibility of a final between two clubs from Argentina. The country supplies four of the last 16 sides, with three of them in the same half of the draw. The Argentine exceptions are Godoy Cruz of Mendoza, who got the knockout phase underway with their match at home to Gremio of Brazil. And the Argentines got off to the worst possible start.

They were a goal down after 40 seconds, falling to one of Gremio's characteristic fluid movements. Centre forward Lucas Barrios headed behind the line, winger Pedro Rocha squared across the face of the goal and midfielder Ramiro arrived to put it home.

It was the only goal of a game where Godoy Cruz huffed and puffed, especially in the second half, but without ever suggesting that they could take real control. Unless they can come up with a major surprise in Porto Alegre next month, the chance of an all-Argentine final will be gone.

Tim Vickery covers South American football for ESPN FC. Follow him on Twitter @Tim_Vickery.